In known multiple-riveting machines a plurality of rivets are fed from a hopper, generally a rotary drum, through tracks to flexible jaws that restrain individual rivets on anvils complementary under striker. The rivets are fed, individually, simultaneously in unison, to the plurality of jaws below the strikers which are laid out in line arrangement of rivets designed for a particular riveted product manufactured by the riveting machine. The members to be riveted together are disposed on the anvils, one member on top of the other member having their rivet receiving holes in vertical alignment. Each rivet is hit by its respective striker and pushed through the aligned holes against the anvil where the rivet is deformed to effect intimate retention of the parts. In one multiple-riveting machine, built to rivet a brake lining to a metal backing, the rivetting pattern is usually set in two rows. In order to reach both rows the rivet feeding system comprises a pair of hoppers and a plurality of vertically aligned, outwardly curved rivet guides. The pair of tracks are oppositely, disposed, one on either side of the strikers, rivet holding jaws and respective anvils comprising the press system. The two hoppers continuously fill each guide with rivets which are retained within the guides so oriented that the head of the rivet is retained within the guide. The body of the rivet projects initially outwardly from the body of press and, subsequently, downwardly and vertically with the head above its body as it is received by the jaws. Each track has a selector member suitably located as to allow passage only of a desired single set of rivets to pass at each stroke of the press to the jaws. Typically, each track system has four to six guides.
In the above feeding assembly of use with a riveting machine, the plurality of rivets from the track fall from the sides and between the jaws out of the guides to directly below the strikers of the press. Only one row of jaws, close to the track per rigid feeding system of the multiple-riveting machine can be filled. Space must be left available above the jaws to permit the plurality of strikers to descend on the rivets and this space must be free of fixed tracking. Thus, one feeding system is able generally to rivet only one row per cycle. In cases where two rows of rivets are desired, a second rivet tracking system on the other side of the machine, as hereinabove described, is used. This duplicate tracking system does not provide for greater ranges and varieties of rivet layout patterns. The fixed to the side track system, hereinabove described, is curved and is prone to distortion, particularly on installation. Such distortion may cause uneven and delayed rivet delivery in operation. Accordingly, installation of such a system requires skilled personnel for the initial setup and subsequent changeovers.
Further, since the head of the sliding rivet is in the track's guide slot, there are friction forces under the head and at the top of the rivet. These forces will be at their maximum when the rivet has to pass the maximum curvature of the track, when the rivet is oriented or positioned horizontally. The longer the rivet the greater the frictional forces present, since the centre of gravity of the rivet moves away from the track and creates a greater moment. As a result, these frictional forces limit the length of the rivet that may be used in order for the rivet to quickly and efficaciously slide down along the track without interference.
Yet further, as there is a gap between the track and the receiving jaws, the rivet, which is leaving the track with a certain speed, sometimes bounces back or falls to the wrong position.
Since the rivets are fed into the jaws from the sides, the jaws must be specially shaped. This results in an additional capital expense.